Upgrading gasoline



SePt- 22, 1959 R. E. ASUTHERLAND I 2,905,619

UPGRADING GASOLINE Filed June 28, 1956 berof the gasoline.

United States Patent Office y 2,905,619 Patented Sept.. 22, `1959 UPGRADING GASOLINE Robert E. Sutherland, Chicago, Ill., assignor, by mesne assignments, to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Application June 28, 1956, Serial No. 594,592

3 Claims. (Cl. 208-64) This invention relates to a novel process for upgrading 'gasoline and more particularly to an integrated process in which a gasoline is separated into selected fractions and the selected fractions are subjected to independent and selected conditions to produce a final product of high octane value.

In order to provide the public with more powerful motor vehicles, the automobile industry is manufacturing engines of greater horsepower and accordingly higher compression ratios. These engines require gasolines of higher octane value in order to operate satisfactorily therein. This, in turn, challenges the petroleum industry to produce gasolines of even higher octane values than the high octane gasolines presently being produced. The present invention provides a novel combination process of mutually related and interdependent steps whereby gasoline is upgraded to these higher octane values.

In accordance with the present invention, a gasoline is fractionated to separate a C6 and lighter fraction and a C7 and heavier fraction. The C7 and heavier fraction is subjected to catalytic reforming to upgrade this fraction of the gasoline. The reformed products are fractionated to separate a C6 and lighter fraction, which fraction is combined with the previously separated C6 and lighter fraction, and the mixture is subjected to isomerization to convert the low octane normal paraiiins into high octane branched parafns. The isomerized products are combined with the reformed products to form a final product of high octane value. p I

Catalytic reforming of gasoline serves to considerably improve its octane value. However, the pentanes contained in the gasoline fraction undergo only minor conversion when subjected to reforming in admixture with the higher boiling gasoline components. Therefore, it

generally is preferred to separate the pentanes from the Igasoline charge and to blend the separated pentanes with the reformed gasoline products. However, the pentanes, as well as the hexanes, contain normal paraffins of low octane number and these paraiiins lower the overall octane value of the final product. In accordance with the present invention, the pentanes and hexanes are fractionated to separate thevhigh octane paraiiins from the low octane parains, and the latter are isomerized into high octane branched chain parains. The high octane paraftns then are blended with the reformed gasoline fraction to produce a final blend of high octane value.

As an illustration of the above, isopentane has a Research octane value, when leaded with 3 cc. of tetraethyl lead, of 103.5. On the other hand, normal pentane has a leaded octane number of only 85. It is readily seen that the presence of the low octane normal pentane in the final gasoline blend reduces the overall octane num- Similarly, normal hexane has a leaded octane number of only 65.3, whereas the branched chain hexanes have leaded octane numbers in excess of 93. Here again, the presence of normal hexane in the final-product considerably reduces the overall octane number of the gasoline. In accordance with the present invention, these low octane components are converted into high octane products and, when blended in the final gasoline, serve to produce a final gasoline of considerably higher octane number thanpreviously attained.

From the heretofore description, it will be noted that the present invention provides an integrated combination yof isomerization and catalytic reforming for the production of high octane gasoline. The high octane product cannot be achieved by catalytic reforming alone, except by using extremely severe operating conditions which, in turn, results in excessive losses in yield, as well as in low catalyst life. These excessive losses and low catalyst life prohibit any practical or commercial utilization ofthe catalytic reforming process in this manner for obvious economic reasons.

It will be noted that the novel process of the present invention selectively separates the low octane components and independently converts them into high octane components. By separating these low octane components and subjecting them to conversion under optimum conditions, improved results are obtained. These improved results include higher overall yields of high octane gasoline. operation of the catalytic reforming at less severe conditions than otherwise would be required, with the concomitant high yields and long catalyst life in the reforming step of the process, the greater exibility in `operation to permit the processing of a variety of Igasoline charge stocks, as well as producing gasolines of even higher octane numbers as may be required to meet market demands of the future. Furthermore, by the novel method of the present invention, the low octane components are converted in the absence of the high octane components, and therefore any possible undesired conversion of the high octane components is avoided.

, The invention is further explained with reference to the accompanying diagrammatic flow drawing which illustrates several specific embodiments thereof. It is understood that the drawing is presented for illustrative purposes and that the scope of the invention is not limited to the specific embodiments illustrated therein.

In the interest of simplicity, the drawing will be described with reference to the particularly preferred embodiment of the invention, to be followed with a description of the alternative, but not necessarily equivalent, embodiments of the invention. The gasoline charge is introduced to the process through line 1 and is directed into dehexanizer 2. In the preferred embodiment, the gasoline charge has a boiling range of from C5 to about 400 F., although the end point may be higher, ranging up to about 450 F. The gasoline charge preferably is a saturated gasoline and thus may comprise straight run gasoline, natural gasoline, etc., or hydrogenated unsaturated gasolines, such as cracked gasoline, Coker distillate, etc., which previously had been subjected to desulfurization-hydrogenation, or a mixture of these gasolines.

In accordance with the present invention, the gasoline charge is fractionated in dehexanizer 2 to separate an overhead fraction comprising pentanes and hexanes, and a bottoms fraction comprising heptanes and higher boiling components, the latter being referred to as C7 and heavier fraction. The C7 and heavier fraction is withdrawn from dehexanizer 2 through line 3 and is subjected to reforming in reforming zone 4.

While reforming zone 4 is illustrated as a single zone, it is understood that this system will comprise heaters, heat exchangers, a series of reaction zones, generally 3 or 4, coolers and receivers. The reforming is effected at a temperature of from about 800 to about 1050 F., at a pressure of from about to about 1000 pounds or more per square inch, a liquid hourly space velocity of from about 0.5 to 10, and in the presence of hydrogen in a mol ratio to hydrocarbon of from about 0.5 to 20.

. line l, a

jiveight 'of the final catalyst. A v`particularly preferred catalyst comprises `a composite of alumina, platinum in a concentration of from about 0.2 to about 1% by Weight and combined halogen in a concentration of from about 0.2 to about 1% by vweightof the nal catalyst. The halogen preferably 'comprises urine and/or chlorine. Other platinum-cntaining catalysts comprise composites of pl'jt'f uhsilica, vplatinum-silicalalumina platinumsilicazirconia pIatinum-silicaialu'mina-zirconia, platinurnsilica-thria, p1atinum-silica-aluminathoria, platinum-s ilica-magnesia, platinum-silicaaluniina-magnesia, etc. Theat'alyst'nay bein the form of powder or larger size granules of irregular size and shape, but preferably is Vthe form of particles of uniform size and shape as obtained by pilling, extruding, the oil drop method, etc. The reforming process produces hydrogen and, in a preferred embodiment of the invention, ythe hydrogen is reeycledd within the system.

The reforn'edprducts are withdrawn from zone 4 through line 5 and are directed to receiver 6. In receiver 6, hydrogencontaining gas is withdrawn through nd while all or a portion may be removed from the process through valve 7, at least a portion of the hydrogen is recycled by way of line 8, valve 8', and line 3 Within the 4system for further use therein.

'I 'he reformed gasoline product is directed from receiver 6 through line 9 into debutanizer 10. In this zone, butanesand lighter products are separated and are withdrawn therefrom through line 11 for further treatment or use as desired. 'I he liquid products are withdrawn from zone through line 12 and are directed to dehexanizer 13. Indehexanizer 13 the C5 and C6 hydrocarbons are separated and are Withdrawn therefrom =through line 1,4 for Yfurther conversion in the manner to be set forth hereinafter. The C1 and heavier reformed products are withdrawn from zone 13 throughuline 15 and, in the'preferred embodiment of the invention, are directed into gasoline blending zone 16'.

The C5 an'dCs hydrocarbons separated in zone 2 are withdrawn therefrom through line 17 and are commingled with the C5 and C6 hydrocarbonswithdrawn fromzone 13 and directed through line 14, the mixture then being directed by way vof line 18 and valve 19 to splitter Z0. Splitter 20 functions to separate an overhead fraction comprising pentanes and a lower fraction comprising hexanes.

The pentanes Yseparated in zone 20 are withdrawn therefrom through line 21 and are directed through line v2.2 toideisopentanizer Z3. The deisopentanizer functions to split an overheadv fraction comprising isopentane from a bottoms fraction comprising normal pentane. It will be noted that zone 23Y functions to separate the isopentane originally containedin the gasoline charge, as well as the isopentane contained in'thereformed products; The isopentane separated in zone 23 is vwithdrawn therefrom through line 24 and, in a preferred embodiment :of the invention,` at least av portion'thereof isdirected to gasoline blending zone 16. 'Isopentane has a leaded Research 'octane number of sfr'abl Component foi' the inal` gasoline blend.

4'lcirr'n'al pentane has a leaded Research octanenumber 'of abut 8 5 and, in order to produce the superv gasolines "of the'presentinvention, is of too low an octane number line hd: "In accordance with thepresent inven- "t1oh,"'thenorriil peiitane fraction is withdrawn "from bout 103 and thus comprises a dedeisopentanizer 23 through line 25 and is directed through valve 26 into pentane isomerization zone 27.

Isomerization zone 27 likewise comprises suitable heater, heat exchanger, reactor, cooler, etc. In a preferred embodiment of the invention, only one reactor will be required because the overall heat of reaction is low. Any suitable isomerizatin catalyst may be utilized in zone 27. AY-preferred catalyst comprises a platinumcontaining composite "and still 4more Yparticularly the alumina-platinurnLcombined halogen 'catalyst described 4above Vfor vuse vin the reforming zone. With thesejcatalysts, isomerization `of pentane generally fis effected at a temperaturejof from aboutf700 toabgutgSOF. and preferably of from about 750 to vabout 850v F., at a pressure of from 'about 50 Vto about 1000 pounds or more per square inch, and more particularly of from about 100 to about 500 pounds per square inch, a liquid hourly space velocity ot from about 0.5 to 5 and va hydrogen to hydrocarbonjratio of frornabout 0.5 toabout In the isomerization reaction, the consumption or p`rodc tion of hydrogen is of very low order andthe hydrogen preferably is recycledwithin theisonierization by well-known means, not illustrated, or it mayfbe supplied, either continuously or intermittently,A from the reforming system. The isomerzed pentane fraction iswithdrawnjrom zone 27 through line 28 and itis returnedbyway of line 22 to deisopentanizer 2 3. Thus, the deisopentanizer serves to separate the isopentaneformed in zone 2 7, as well as the isopentane'contained in the originalgasoline charge and that produced in the reforming reaction. As hereinbefore set forth, the isopentane is directed through line 24 into gasoline blendingzone 16 pentane is withdrawn from the lower portion of zon e 23 recycled in zone 27 for isomerizaaluminum chloride, aluminum bromidetzino chloride,

etc., along with the corresponding jhydrogenbalide. In one embodiment, the metal halide catalystsare cornposited with a suitable carrier such asjalurnina, bauxite, clay, etc., and utilized as a fixed bedofcatalyst in the reaction zone. However, it is understood that A these catalysts may be utilized in liquid form, When utilizing these catalysts, the isomerization reactiongenerallyis effected at a temperature of from about to abo ut 300 F. It is understood that the various isomerization catalysts are not necessarily equivalent and that the preferred catalyst comprises the platinum-containing catalyst hereinbefore described.

Regardless of the particular isomerization system employed, operating conditions are selected so` that the isomerization reactionwill b e selective, with a minimum of cracking or other side reactions. By separately subjecting the pentane fraction to isomerization in an independent zone under optimum conditions for this reaction, and with th'e recycle operation illustrated, substantially complete isomerization of the'normal vpentane to 1 isopentane maybe effected in the present process. As hereinbefore set forth, this serves toreduce the amount of normal pentane in the final gasoline product to a minimum. In contrast thereto, it has ,been found that the inclusion of the pentanes in the gasoline charge' to reform- `e included Vin any substantial-`quantities in the iinal ing 'eifectsvery little isomerization of the zno'rnialpentanes to isopentanes.

The hexanes separated in'splitter 20 are withdrawn rherefram'through line 7.9 and are airectedt aeisfoheiranizer. vIn deisoheiraniz'er v30,'lliwyv octneori'ral has@ sarees as a; @was finden vfam, naar boiling higher octaneV bra and, in the preferred embodiment of the invention, at least a portion thereof is directed to gasoline blending zone 16. Here again, it will be noted that the deisohexanizer serves to separate the lower boiling higher octane branched chain hexanes originally present in the gasoline charge to the process, as well as that produced in the reforming step of the process.

The normal hexane and higher boiling C6 components are withdrawn from zone 30 through line 32. and are directed through valve 33 to isomerization zone 34. In zone 34, the hexanes are subjected to isomerization under optimum conditions which are independently controlled to obtain maximum conversion. This isomerization zone will be similar to that hereinbefore described in connection with the pentane isomerization, and may utilize the same type of catalyst hereinbefore described. Here again, it is preferred that the catalyst comprises the platinum-containing composite hereinbefore described. However, the conditions in this zone, while being within the range hereinbefore described, will be selected to effect maximum conversion to the desired products.

In a preferred embodiment of the invention, the isomerization products from zone 34 are withdrawn from line 35 and are directed through valve 36 to gasoline blending zone 16. Depending upon the particular gasoline charged to the process, the isomerized product from zone 34 will contain cyclic compounds including methyl cyclopentane, cyclohexane, benzene, etc., in small but varying concentrations. These cyclic compounds are of high octane value and, in the preferred embodiment of the invention, are included in the final gasoline product of the process. The features of once through operation of the reforming, recycle operation in the pentane isomerization and once through hexane isomerization all combine to produce a final gasoline product of high octane number, without the necessity of utilizing complicated and expensive equipment and processes to separate the diiferent type compounds present in the eflluent products from these zones.

From the above description, it will be noted that the nal gasoline blend comprises reformed gasoline, isopentane, low boiling high octane branched chain hexanes and isomerized hexanes. As another advantage of the process of the present invention, the gasoline blend is of low vapor pressure and therefore will permit the introduction of butanes and additional isopentanes to raise the vapor pressure to the desired pounds R.V.P. or thereabouts. The introduction of these materials further increases the octane rating of the final gasoline product. Depending upon the particular charge, the final gasoline blend will have a leaded Research octane number of above 95 and may range up to 102 or even higher. Of equal importance is the fact that the integrated process of the present invention produces a total pool gasoline in a yield of from 6 to 10% or more greater than obtainable by prior methods. It is apparent that this increase in yield of high octane gasoline is of extreme importance from a commercial consideration.

In conventional fractionation, a small amount of hexanes will be carried over in the overhead fraction from splitter and will accumulate in the bottoms fraction in deisopentanizer 23. In order to avoid the buildup of the hexanes in this step of the process, a drag stream of the bottoms fraction is continuously or intermittently directed through line 27 and valve 38 to be returned by way of lines 39 and 19 to splitter 20. In this manner, the hexanes will be removed from the C5 fraction and will not build up in the pentane isomerization system.

The process flow hereinbefore described comprises the particularly preferred method of operation. The drawing also illustrates several alternative, but not necessarily equivalent, operations which may be utilized within the broad scope of the present invention. While it is preferred to separately isomerize the C5 fraction and the C6 fraction, in some cases it may be satisfactory to effect the isomerization of the C5s and Cs in a single isomerization zone. In this embodiment, the pentanes and hexanes may be directed through line 18, line 40, valve 41, line 32 and line 33 to isomerization zone 34. While the isomerization products may be directed through line 35 and valve 36 to gasoline blending zone 16, in another embodiment the isomerization products are directed through line 42, valve 43 and line 19 to splitter 20. Here again, the splitter serves to separate pentanes from hexanes and the former is directed to deisopentanizer 23, while the latter is directed to deisohexanizer 30. The bottoms fraction from -both of these fractionators are returned to the isomerization zone. This is accomplished by passing the bottoms from zone 23 through line 25, line 44, valve 45 and line 32 to zone 34, and passing the bottoms fraction from zone 30 through line 32 and valve 33 to zone 34. As hereinbefore set forth, the use of a single isomerization zone for converting both the pentanes and hexanes generally is not as desirable as employing separate zones for these isomerizations. However, in some cases, the octane value of the nal gasoline will be suicient to meet prevailing market requirements and therefore the use of a single isomerization zone may be satisfactory.

In another embodiment of the invention when utilizing a single isomerization zone, the pentane-hexane fraction being directed through line 18 is passed through valve 19 into zone 2t), and subjected to separation therein as well as in deisopentanizer 23 and deisohexanizer 30. However, the normal pentane is directed through lines 25, 44 and 32 to isomerization zone 34, instead of being subjected to separate isomerization as in the particularly preferred embodiment of the invention.

In still another embodiment, when employing a separate isomerization zone each for the pentane and hexanes, and recycling of the hexanes is utilized, the effluent isomerization products from 'zone 34 are directed through lines 35, 42 and 46, valve 47 and line 29 and deisohexanizer 30 for separation of the low boiling high octane branched chain hexanes from normal hexane, the latter to be recycled by way of line 32 to zone 34 for further isomerization.

When utilizing recycle type operation of the isomerized hexanes, there may be a buildup of heptanes in deisohexanizer 30. This is similar to the possible buildup of hexanes in deisopentanizer 23 heretofore described. In order to prevent the buildup of heptanes in zone 30, a drag stream is directed by way of line 48, valve 49 and line 1 to dehexanizer 2. In dehexanizer 2 the heptanes will be concentrated in the bottoms fraction and subjected to reforming as part of the charge thereto. The hexanes will be recycled to isomerizer 34 by the circuit heretofore described.

When utilizing recycle type operation of the hexane isomerization products, there is a possibility of the presence of cyclic compounds which may interfere with fractionation in zone 30 and possibly in Zones 20 and 23. It is within the scope of the present invention to remove the cyclic compounds in any suitable manner, not illustrated, as for example by subjecting the isomerized products to extraction with a solvent which selectively removes the cyclic compounds and particularly the aromatics. As hereinbefore set forth, the necessity for such treatment is avoided in the particularly preferred embodiment of the invention in which the isomerized products from zone 34 are supplied directly to gasoline blending zone 16.

Although not illustrated in the drawing, in another embodiment of the invention, additional fractionating zones may be provided to split the heptanes into high yoctane low boiling components and low octane high boiling componentsand the separated high boiling heptane fraction may be subjected to isomerization in the `raramente saine orjdiffernt nzone vor zenesrrmthat used for "lsomer'izing the pentanes and/or hexan'cs. 'In vthis embodiment, fractionating zones "2` "and 13 will vfunction tseparateiCg CS 'and .C7 from C8 :and heavier compo- "h'ei'its -Thefpentane's'will be separated from vthe hexanes V'iiigzon'e will Acomprise C8 'and heavier.

."I'n'theinterest of simplicity, heaters, Vheat exchangers, cookers, condensers, pumps, receivers and similar jap- Vpfuitenanes'have beenv omitted from the drawing. These details are well-known the art'an'd are not required for inrderstarding 'the present invention. Similarly, de-

ofthe'internals'oi the frfactionating zones have been omitted, `it being understood .that any suitable trays, side- "ofside pans, lbub'lfledecks, etc. will be employed to bbtain separation of Athe vcharge `and `intermediate 'fractions into the "desired components.

rAs hereinbefore set' forth, the novelprocess of the --present'invention produces a rhigh `yield of high octane 4gasoline product, which product iiswithdrawn from the k:process:through line V50. The linalg'asoline product will ,have'a Researchleaded octanenumber above95 and up to 102 or more. Anotheradvantage to the process of thepresentinventionis that the severity of the reforming operation is lower than otherwise would be required to yre`a`.ch this high octane product in the absence of the isomerizationfsteps of the process Therefore, the yield obtained in 'thereforming operation is considerably increased and the lie of the reforming catalystis considerably extended. Of utmost importance is the fact that the process of the present invention produces this high octane gasoline product with an increase in yield of 6 Ato 10% or more, over and above that previously attainablc.

`jThC following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

Example I example illustrates the advantages of the present invention when processing Arabian straight run gasoline hailing a boiling range of from 2 04 u to 362. F., an API gravity of 57.9 and a Research clear octane number of 34. l The octane number of the total gasoline product to b e obtained is 98 Research leaded.

On lthe basis of charging 10,000 barrelsper day, the gasoline ishsplit into 2,200 barrels per day of C and C6 and 7,800 barrelsper daypf C7 and heavier. The C5 and C6 fraction is further split into 1 ,l00 barrels per day each of a C5 fraction and of a C5 fraction.

The Cf; andheavier fraction is subjected to reforming in the presence of a catalyst comprising alumina, about (14% by weight of platinum and about 0.5% by weight of combined halogen, ythe lattercomprising about 0.3% by weightof combined uorineandabout 0.2% by Weight of combined chlorine. The reforming is eiected in a 'series of 3 -catalyst-containing reactors with intervening heating ofthe reactor effluents between reactors. The

chl'ngewto reforming is introduced into the reaction zone at a Vtemperature of about 895 F., and at a space velocity of about 2.5. The reactors are maintained at a Apressnrebfabout 500 pounds per square inch, and hydrogen is recycled to'mintain a hydrogen to hydrocarbon ratio .catalytic reforming alone is usedV and is severity tofproduce, a ,98 leaded octane number product,

o fil. Other portions 'of the'same catalyst are used in the "pentane isomer'ization and hexane isomerization zones Thepentane isomerizationis eiected at a temperature of 785 F., a pressure of 310 pounds per square inch, while utilizing a hydrogen to hydrocarbon ratio of l :1. The 'hexane isomerizationjis effected at a teniperature of 760 F., apressure'of 310 pounds per square "n'ch, While utilizing a hydrogen to hydrocarbon ratio of From the above operation, there is produced a total C5 `and heavier gasoline product of 8,400 barrels per day, which is an 'overall yield of 84%, based on 'the original A'gasoline charge. In contrast, in an operation in which increased 'in the' overall yield is '7.,410 barrels perdayor 74.1%, based yon the Voriginalgasolinecharge. ,It will benotedthat 990A barrels "perday of additional gasolineprodnctiis produced through the use of thevpr'ocess of the present invention.

. Example II 'fln an operation similar to 'thatdescribed in'Ex'ample I but utilizing a Wyoming straight Vrun-gasoline charge and Ioperating to produce'a leaded (Research octane product r(5h97, opierat'ionin accordance with the present invention yields 1,010 ddi'tionl`birrel`s-iper dayof 97 `o'ctane gaso- `li s'compared to catalytic reforming lalone at a severity 'necessary to achieve Vvtlii's'octarie product. The Wyoming Vstraight run g'e'fsoliri'e has a boiling 'range of 210 to 400 R, 'an 'AEI tvgravity fof 56.4 and "a Research 'clear octane er of 52.5. 'It is split into 1,5670 barrels per day of alpen ne'fraction, 1,920 barrels per day of a hexane 'fraction and a heavier fraction, reforming said heavier 'fraction 'aiifd separating from the resultant products a fraction anda 'reformedgasoline fraction, combinirlg'ls'aid CC'fractions -'and 'spli'ti'ng thefrcsultant mixtu'r'efinto 'a fraction ainda C6 fraction, Vseparately fractiona'ting said `C'5'fraction 'and said C6 fraction to sepaormal'pentan'e and branched chain 'he'xa'nes 'from normal hexane, subjecting the th'us separated normal pentane 'and normal hexane ito catalytic isomeriztin', 'conmlngling resultant isomerized products with portions," at least, of sai'd reformed gasoline `fraction, 'said isopent'aric and "said branched. chain hexanes, and recovering the resultant blend as said high 'octane number motor fuel.

2. The'pro'cess of claim 1 further characterized in that said normal 'penta'ne and `said normal hexane are isome'rized in admixture. A

`3. The process `of claim 1 further characterized in that said normal pentane and :said normal hexane are sep'arately isomerized.

VlieferencesiCited inthe ile of this patent entran `sri/nas PATENTS lllvering v June 22, 1948 z'asz'l nchst-.1; ran. 4, 1.9 55 intenser etai. Apr; 3, 1956 

1. A PROCESS OFR PRODUCING HIGH OCTANE NUMBER MOTOR FUEL FROM LOW OCTANE NUMBER GASOLINE WHICH COMPRISES FRACTIONATING SAID GASOLINE TO SEPARATE THEREFROM A C5-C6 FRACTION AND A HEAVIER FRACTION, REFORMING SAID HEAVIER FRACTION AND SEPARATING FROM THE RESULTANT PRODUCTS A C5-C6 FRACTION AND A REFORMED GASOLINE FRACTION, COMBINING SAID C5-C6 FRACTIONS AND SPLITING THE RESULTANT MIXTURE INTO A C5 FRAACTION A C6 FRACTION, SEPARATELY FRACTIONATING SAID C5 FRACTION AND SAID C6 FRACTION TO SEPARATE ISOPENTANE FROM NORMAL PENTANE BRANCHED CHAIN HEXANES FROM NORMAL HEXANE, SUBJECTING THE THUS SEPARATED NORMAL PENTANE AND NORMAL HEXANE TO CATALYTIC ISOMERIZATION, COMMINGLING RESULTANT ISOMERIZED PRODUCTS WITH PORTIONS, AT LEAST, OF SAID REFORMED GASOLINE FRACTION, SAID ISOPENTANE AND SAID BRANCHED CHAIN HEXANES, AND RECOVERING THE RESULTANT BLEND AS SAID HIGH OCTANE NUMBER MOTOR FUEL. 